Froth flotation of iron sulfide ore



Patented Sept. 28, 1954 FROTH FLOTATION OF IRON SULFIDE ORE Arvid Emil Anderson, Cornwall, Pa., assignor to Bethlehem Steel Company, a corporation of Pennsylvania No Drawing. Application November 14, 1951, Serial No. 256,398

1 This invention relates to the recoveryof metal sulfides by froth flotation, and'more particularly to the recovery of sulfides by the use of xanthate reagents in emulsified form.

The principal object of this invention is the recovery of metal sulfides by means of an improved type of flotation reagent.

Another object is to provide a flotation reagent composition which will recover iron pyrites more rapidly and more completely than has been possible heretofore.

A further object is to retardthe decomposition of aqueous xanthate solutions by producing a xanthate emulsion.

Iron pyrites, or iron sulfide ores, are accompanied by considerable gangue material, and the most feasible means of separating the iron sulfide is by use of a froth flotation process. In certain types of magnetite ores, which also contain economically recoverable quantities of chalcopyrite and iron pyrites, the magnetic iron oxide and chalcopyrite are first removed sequentially by well known means. After removal of the iron oxide and chalcopyrite, a pulp remains which contains largely iron pyrites and gangue. To remove the iron pyrites in relatively pure form from the pulp, and thus free it from gangue and any metal values contained therein, the pulp is subjected to a froth flotation process which usually comprises first, a treatment with copper sulfate solution to produce a clean, reactive, surface on the exposed particles of pyrites contained in the pulp.

Secondly, the pulp is subjected to predetermined amounts of a collector material, such as sodium ethyl xanthate, and a frother, such as pine oil.

In this manner, commercially useful iron pyrites can be obtained.

In the method just described, the collector and frother must be added separately. I have found that by combining the collector and frother in an emulsion, made with special emulsifying agents, not only is the addition ofthe flotation reagents made with greater facility, but also there is a considerable gain in flotation efiiciency. I;

have found that this increased flotation efficiency is obtained by emulsifying the alcohol xanthates and a irother material, such as, pine oil with waxy polyoxyethylene lauryl alcohol, and adding the emulsion so made directly to the flotation pulp. By use of my improved reagent emulsion, in place of the reagents being added separately, I have been able to obtain a definite increase in recovery of concentrate.

In order to produce a quantity of my emulsion which will yield an adequate supply'and be convenient to handle, 250 pounds of sodium ethyl xanthate and 250 pounds of potassium ethyl 6 Claims. (Cl. 209166) oilto 1.

xanthate are dissolved in water to yield about 225gallons of solution. Another solution is made by dissolving 756 grams of polyoxyethylene lauryl alcohol in about two gallons of warm water. A quantity of from 10 to 30 gallons of xanthate solution is pumped thru a homogenizer, for example, a homogenizer of the Marco Flow-Master type, and the polyoxyethylene lauryl alcohol solution added to the xanthate slowly during the pumping operation. The solution thus produced is mixed with from 3 /2 to 15 gallons of G. N. S. No. 5 pine oil containing gallon of pine tar residue. The resultant solution is then pumped thru the homogenizer, set at a pressure of 250 to 700 p. s. 1., until a good emulsion is made and this emulsion is then dispersed thru the remainder of the xanthate solution by pumping the total solution thru the homogenizer. In this manner a stable emulsion can be produced which will retain its collector properties when added to large quantities of pulp in the flotation machines.

It should be noted that while the amounts given in the foregoing description for the preparation of the emulsion have proved quite satisfactory, it is notrequired that the proportions given be rigidly adhered to. Considerable variation of the proportions of ingredients is permissible, the desideratum being, of course, selection of quantities of reagent and emulsifier which will form a stable and acceptable emulsified xanthate flotation reagent under the particular conditions in which it may be used. Illustrative of the variation of quantities permitted in the production of the emulsified reagent is the case of pine oil. As has been mentioned, pine oil may be added, in the example given, in quantities ranging from 3 to 15 gallons, for the amount of pine oil needed will vary with the operating requirements. Likewise, it is not intended that the amount of polyoxyethylene lauryl alcohol used to make the emulsion should be held to any arbitrary limit. The amount of emulsifier needed to produce a satisfactory emulsion can best be determined by a simple series of tests to meet individual requirements.

In the preceding example, it is to be noted that a mixture of, sodium ethyl xanthate and potassium ethyl xanthate has been used in the ratio given, has proved to be the most efficient, excellent results can be obtained with difierent proportions of the two xanthates than the one given. Moreover, it is not necessary to use a mixture of potassium and sodium ethyl xanthates, for either one of the xanthates used alone in an 3 amount of 500 pounds (for the example shown) will prove satisfactory.

While the mixture, at the specific ratio The type of polyoxyethylene lauryl alcohol useful in producing my emulsion is that form of the compound which has a specific gravity of from 1.18 to 1.22, and is a waxy appearing compound.

While so far I have mentioned only pine oil and pine tar residue as the frothing ingredient, any frother satisfactory in sulfide flotation, which is symbiotic with the other ingredients in the emulsified state, may be used. Any of the products known as wood creosotes, which result from the distillation of hard or soft woods, will operate as satisfactory frothers in my flotation emulsion. By wood creosotes I mean to include any of the oily components found in either the distillate or the tarry fractions in the residue after distillation. Typical examples of wood creosotes are, pine oil, pine tar and pine tar oil.

Collectors which may be used in forming the emulsion are sodium ethyl xanthate, sodium propyl xanthate, potassium ethyl xanthate and potassium propyl xanthate. I have found that enhanced recovery of concentrate is obtained when using an emulsion made up with a mixture of sodium ethyl xanthate and potassium ethyl xanthate, preferably in the ratio of 1 to 1, over the results obtained when only a single xanthate is'used in the emulsion.

It is well known to use xanthates of some of the higher alcohols as collectors in flotation processes, and while the added cost of such higher alcohol xanthates makes them less to be preferred than the xanthates already mentioned, it is intended that the higher alcohol xanthates, which are operable as collectors with iron. sulflde ores and are amenable to emulsification, should come within the spirit of my invention. Of the higher alcohol xanthates, the butyl and amyl xanthates, especially, are effective in my emulsion. The higher alcohol xanthates are particularly useful in the treatment of arsenopyrites, as well as in treating copper and lead sulfides.

When treating sulfide ores, or pulps, a knowledge of the nature of the ore to be treated is of course necessary in order to obtain the most efficient separation in the flotation process. Keeping this fact in mind, a satisfactory reagent emulsion can be prepared for any kind and condition of sulfide ore. In performing the actual flotation separation, pulp is introduced into the flotation machine in the usual manner and flotation reagent emulsion is added to the pulp slowly. The amount of emulsion added may range from an equivalent of 0.1 pound to 0.5 pound of xanthate per ton of dry ore treated.

I have found that changes in temperature of the pulp, when using the emulsion, do not affect the flotation of the sulfides as markedly as when the xanthate and pine oil are added separately.

Depending on the nature of the ore, and the particular conditions under which the flotation is performed, it may in some cases be desirable to add additional frother to the system. When additional frother is added, the pulp is subjected to my flotation emulsion in the manner previously described, and separate additions of frother are then made as required. When frother is added separately, and in addition to that frother material already in the emulsion, the additional frother may be of any substance normally used as a frothing agent in the separation of sulfide ores.

The following examples indicate results for the recovery of concentrates obtained when using my emulsion as against results when using reagents in non-emulsified form, as well as results from the use of mixed xanthate emulsion and single xanthate emulsion.

EXAMPLE I A portion of iron pyrites pulp, resulting from extraction from a magnetite ore, to which copper sulfate had been added, was treated with an emulsion of sodium ethyl xanthate,. pine oil and polyoxyethylene lauryl alcohol in proportions equivalent to 0.15 pound of xanthate and 0.02 pound of pine oil, per ton of feed, in a laboratory size flotation machine. The froth was removed by skimming for a total of 2 /4: minutes. It was filtered, dried, weighed and analyzed. for sulfur. A comparative test fusing a similar pulp was run wherein the xanthate and pine oil were added separately in the same equivalent amounts. The results of these two tests are presented as follows:

Polyomyethylene lauryl alcohol emulsion The foregoing example indicates a considerable gain in recovery of concentrate when emulsion is used, and this gain is believed to be attributable to the fact that the emulsion enhances the stability of the xanthate, and develops a more nearly complete dispersion of the collector and frother than can possibly be attained when collector and frother are added separately.

In the tables, sulfide ore, in the respective feed, tailing and concentrate, is recorded as yield of sulfur (S) EXAMPLE II A sodium ethyl xanthate, pine oil-pine tar residue, polyoxytheylene lauryl alcohol emulsion was prepared and used in a pyrite flotation plant for four consecutive days. In a similar manner, a mixture of equal parts of sodium and potassium 1 ethyl xanthates were made into a pine oil-pine tar residue, polyoxyethylene lauryl alcohol emulsion. The mixed xanthate emulsions were used in the pyrite flotation plant for four days direct- 1y following the test with the sodium ethyl xanthate emulsion. The results of this plant test work are presented in the following tables.

Polyozcyethylene lauryl alcohol emulsion with single wanthate Polyomyethylene lauryl alcohol emulsion with mixed xanthates Percent Product by Pergent Yled of weight Concentrate 6. 37 51. 40 77. 0 Tailing 93. 63 1. 04 23.0 Feed 100 4. 25 100 I claim:

1. A method of concentrating iron sulfide ore which comprises pulping the ore adding to the ore pulp an emulsion comprising polyoxyethylene lauryl alcohol (specific gravity 1.18-1.22) a collector of the group consisting of sodium ethyl xanthate, sodium propyl xanthate, potassium ethyl xanthate, potassium propyl xanthate and mixtures thereof, and a wood cerosote frother, and subjecting the pulp to a froth flotation operation.

2. A method of concentrating iron sulfide ore which comprises pulping the ore adding to the ore pulp an emulsion comprising polyoxyethylene lauryl alcohol (specific gravity 1.18-1.22), sodium ethyl xanthate and a wood creosote frother, and subjecting the pulp to a froth flotation operation.

3. A method of concentrating iron sulfide ore which comprises pulping the ore adding to the ore pulp an emulsion comprising polyoxyethylene lauryl alcohol (specific gravity 1.18-1.22), a mixture (1 to 1) of sodium ethyl xanthate and potassium ethyl xanthate, and a wood creosote frother, and subjecting the pulp to a froth flotation operation.

4. A method of concentrating iron sulfide ore which comprises pulping the ore adding to the ore pulp an emulsion comprising polyoxyethylene lauryl alcohol (specific gravity 1.18-1.22), sodium propyl xanthate and a wood creosote frother, and subjecting the pulp to a froth flotation operation.

S. A method of concentrating iron sulfide ore which comprises pulping the ore adding to the ore pulp an emulsion comprising polyoxyethylene lauryl alcohol (specific gravity 1.18-1.22), potassium ethyl xanthate and a wood creosote frother, and subjecting the pulp to a froth flotation operation.

6. A method of concentrating iron sulfideore which comprises pulping the ore adding to the pulp an emulsion comprising polyoxyethylene lauryl alcohol (specific gravity 1.18-1.22) sodium ethyl xanthate and pine oil, and subjecting the pulp to a froth flotation operation.

References Cited in the file of this patent UNITED STATES PATENTS Name Date Schoeller et a1 Aug. 21, 1934 OTHER REFERENCES Number 

1. A METHOD OF CONCENTRATING IRON SULFIDE ORE WHICH COMPRISES PULPING THE ORE ADDING TO THE ORE PULP AN EMULSION COMPRISING POLYOXYETHYLENE LAURYL ALCOHOL (SPECIFIC GRAVITY 1.18-1.22), A COLLECTOR OF THE GROUP CONSISTING OF SODIUM ETHYL XANTHATE, SODIUM PROPYL XANTHATE, POTASSIUM ETHYL XANTHATE, POTASSIUM PROPYL XANTHATE AND MIXTURES THEREOF, AND A WOOD CREOSOTE FROTHER, AND SUBJECTING THE PULP TO A FROTH FLOTATION OPERATION. 